1. Field of the Invention
The present invention relates to a zoom lens.
2. Description of the Related Art
In recent years, various types of electronic imaging apparatuses have become widespread. A majority of such electronic imaging apparatuses include a zoom lens as an imaging lens. Size reductions of recent electronic imaging apparatuses together with further size reductions of the zoom lenses continue to be demanded and to meet these demands, many compact zoom lenses have been proposed.
In particular, monitoring cameras used for closed circuit television (CCTV) use visible light during the day and near infrared light at night. Thus, compact zoom lenses capable of handling a spectrum from visible light to near infrared light have been proposed as monitoring camera lenses (see, for example, Japanese Patent No. 3600870 and Japanese Patent Application Laid-Open Publication No. 2004-317901).
Wide angle, large diameter zoom lenses capable of monitoring a wider area in a dimly lit area are preferable as monitoring camera lenses. Further, increases in the number of megapixels of imaging elements (CCDs, CMOSs, etc.) has progressed and in terms of capturing even finer characteristics of an object, that is to say, with respect to a lens capable of handling higher megapixels, expectations are high. Moreover, demand is increasing for zoom lenses that are more compact and applicable for use with compact, monitoring-use dome cameras that have come into widespread use.
Meanwhile, to capture even finer characteristics of an object, lenses for megapixel imaging apparatuses must sufficiently correct various aberrations occurring near the image plane.
Although the zoom lenses disclosed in Japanese Patent No. 3600870 and Japanese Patent Application Laid-Open Publication No. 2004-317901 are able to handle megapixel imaging elements to a certain degree, with respect to various type of aberration, such as longitudinal chromatic aberration and spherical aberration, correction is difficult. Hence, the lenses are not suitable for use with megapixel imaging apparatuses.